Roberts R707 quiet on Long waveband? - UK Vintage Radio Repair and Restoration Discussion Forum

GJR 11L · 30th Jun 2009, 4:44 pm

The set has recently been thoroughly restored, I even dared to venture inside those dreaded modules as it came here dead. Result is that now, although it works perfectly on FM and manages to pick up a surprising number of listenable-to SW broadcasts, MW is a little quieter than FM, LW significantly so.

Now, as I currently don't have another, working 707 in the house, I cannot remember what the last one was like as a comparison.

Stations on all bands are where they should be following my repairs, there's no problem receiving anything, and if I'm told that "they all do that", then I'll be fine with that, though I'm sure that my last one was, if anything, slightly louder on the MW and LW bands for a given volume setting than on FM.

Every cap and most resistors were replaced when the work was done, anything that was even slightly off its correct value in fact.

So, do I live with it and stop worrying so much?
Do I take it apart again and attend to something that will appear so obvious when it's pointed out that I'll want to kick myself?

Any suggestions would be most welcome.

Thanks in advance, everyone.

Steve_P · 30th Jun 2009, 4:52 pm

Clean the wavechange switches first - as always. Check the switches thouroughly.

Sometimes after the AF117 treatment the alignment sometimes goes off. Especially after taking the silicon route,

Cheers,

Steve P.

Mike Phelan · 30th Jun 2009, 5:11 pm

My last one wasn't that bad on LW, John.
I'm probably teaching my predecessor to apply ova to her anatomy, but can see if the front-end is OK by sliding the LW coil around on the ferrite rod for a peak.

Hope you don't have to open any cans again!

wireful3 · 30th Jun 2009, 5:16 pm

As the problem is on LW and MW I would guess the same as Mike and look at the ferrite rod coils.. Mine is certainly a bit louder on MW than FM.

ronbryan · 30th Jun 2009, 5:24 pm

I have had problems with the band switch assembly on one R707. Plated through holes are used to link top and bottom side copper layers and several had failed. Try selecting LW and confirming that the various LW switched connections are working end to end.

Ron

GJR 11L · 30th Jun 2009, 11:04 pm

Thanks for the ideas, chaps.

Steve_P, I used AF125s in there, and while these haven't given me any alignment issues in other sets when AF11* has been replaced by AF12*, I did consider that these transistors may not be a precise match in every way for the originals. So I took the set into work a couple of days ago and had one of the students in a colleague's tutor group take a look as an exercise in correct use of the equipment!
This exercise in attempting to inspire an interest in old tech among the younger folk showed me that, in fact, everything was fine in terms of alignment.

Mike, I'd never accuse you of giving me unsolicited tuition in egg-sucking, I've learnt a great deal from you as I have from this forum generally. I wouldn't dream of dismissing anyone's good advice so lightly.

Let us just say that I expect to be kicking myself by the end of this exercise, I've been otherwise occupied for a good while and some things, it appears, one can forget.

I shall report my findings when I manage to find the time again.

& yes, I too hope that I don't have to open those evil things again for a very long time!

30th Jun 2009, 4:44 pm	#1
GJR 11L Heptode Join Date: May 2004 Location: Ellington, Northumberland, UK. Posts: 815	Roberts R707 quiet on Long waveband? The set has recently been thoroughly restored, I even dared to venture inside those dreaded modules as it came here dead. Result is that now, although it works perfectly on FM and manages to pick up a surprising number of listenable-to SW broadcasts, MW is a little quieter than FM, LW significantly so. Now, as I currently don't have another, working 707 in the house, I cannot remember what the last one was like as a comparison. Stations on all bands are where they should be following my repairs, there's no problem receiving anything, and if I'm told that "they all do that", then I'll be fine with that, though I'm sure that my last one was, if anything, slightly louder on the MW and LW bands for a given volume setting than on FM. Every cap and most resistors were replaced when the work was done, anything that was even slightly off its correct value in fact. So, do I live with it and stop worrying so much? Do I take it apart again and attend to something that will appear so obvious when it's pointed out that I'll want to kick myself? Any suggestions would be most welcome. Thanks in advance, everyone. __________________ John.

30th Jun 2009, 4:52 pm	#2
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: Roberts R707 quiet on Long waveband? Clean the wavechange switches first - as always. Check the switches thouroughly. Sometimes after the AF117 treatment the alignment sometimes goes off. Especially after taking the silicon route, Cheers, Steve P. __________________ If we've always had it, why is the Car Boot open? You're not sneaking another Old TV in are you...?

30th Jun 2009, 5:11 pm	#3
Mike Phelan Dekatron Join Date: Nov 2003 Location: Near Leeds, West Yorkshire, UK Posts: 4,609	Re: Roberts R707 quiet on Long waveband? My last one wasn't that bad on LW, John. I'm probably teaching my predecessor to apply ova to her anatomy, but can see if the front-end is OK by sliding the LW coil around on the ferrite rod for a peak. Hope you don't have to open any cans again! __________________ Mike.

30th Jun 2009, 5:16 pm	#4
wireful3 Retired Dormant Member Join Date: Sep 2003 Location: Bristol, UK. Posts: 808	Re: Roberts R707 quiet on Long waveband? As the problem is on LW and MW I would guess the same as Mike and look at the ferrite rod coils.. Mine is certainly a bit louder on MW than FM.

30th Jun 2009, 5:24 pm	#5
ronbryan Octode Join Date: Jan 2003 Location: Guildford, Surrey, UK. Posts: 1,959	Re: Roberts R707 quiet on Long waveband? I have had problems with the band switch assembly on one R707. Plated through holes are used to link top and bottom side copper layers and several had failed. Try selecting LW and confirming that the various LW switched connections are working end to end. Ron

30th Jun 2009, 11:04 pm	#6
GJR 11L Heptode Join Date: May 2004 Location: Ellington, Northumberland, UK. Posts: 815	Re: Roberts R707 quiet on Long waveband? Thanks for the ideas, chaps. Steve_P, I used AF125s in there, and while these haven't given me any alignment issues in other sets when AF11* has been replaced by AF12, I did consider that these transistors may not be a precise match in every way for the originals. So I took the set into work a couple of days ago and had one of the students in a colleague's tutor group take a look as an exercise in correct use of the equipment! This exercise in attempting to inspire an interest in old tech among the younger folk showed me that, in fact, everything was fine in terms of alignment. Mike, I'd never accuse you of giving me unsolicited tuition in egg-sucking, I've learnt a great deal from you as I have from this forum generally. I wouldn't dream of dismissing anyone's good advice so lightly. Let us just say that I expect to be kicking myself by the end of this exercise, I've been otherwise occupied for a good while and some things, it appears, one can forget. I shall report my findings when I manage to find the time again. & yes, I too hope that I don't have to open those evil things again for a very* long time! __________________ John.